Japanse sierkers

Prunus serrulata 'Kanzan'

Engels: Japanese Cherry

treeRosaceae

Japanse sierkers (Prunus serrulata 'Kanzan') is a tree from the Rosaceae family that grows up to 10 meters tall. This plant thrives in full sun and requires low maintenance. Blooms in spring with pink flowers and attracts bees and butterflies.

Hoogte

600–1000 cm

Breedte

500–800 cm

Zonligging

full sun

Waterbehoefte

moderate

Grondsoort

loam, clay soil, chalky soil

Onderhoud

low maintenance

Bloeitijd

spring

Bloemkleuren

pink

Ecologische waarde

Trekt bijen aan

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Care tips

Planting

Japanese cherry 'Kanzan' is best planted as a bare-root or container-grown tree in October, November or March, when the soil is workable and the tree is dormant or just breaking dormancy. Choose a position in full sun with plenty of space—this cultivar will reach 6–10 metres tall with a spread of 5–8 metres, so plant at least 7 metres from buildings, boundaries and other large trees. The tree tolerates a wide range of soils including loam, clay and chalky ground, but drainage must be reasonable. Avoid waterlogged sites. Before planting, dig a hole roughly twice the width of the root ball but no deeper—the root flare (where the trunk widens at the base) should sit at or just above soil level. Break up compacted soil at the base and sides of the hole to encourage roots to spread. If your soil is heavy clay, fork in some grit or coarse organic matter to improve structure, though 'Kanzan' copes well with clay if it isn't sodden. Position the tree so the stem is vertical, backfill with the excavated soil, and firm gently with your heel to eliminate air pockets. Water thoroughly after planting—give at least two full watering cans even if the soil seems moist. Drive in a single vertical stake at a 45-degree angle or use an upright stake on the windward side, securing the trunk with a tree tie and spacer to prevent rubbing. Apply a 5–8 cm layer of well-rotted compost or bark mulch around the base, keeping it clear of the trunk itself, to suppress weeds and conserve moisture while the roots establish.

Pruning

Prune Japanese cherry 'Kanzan' only in June or July, when the tree is in full leaf and sap is flowing freely. Pruning during the dormant winter months invites silver leaf disease and bacterial canker, both serious problems for Prunus species. The summer timing allows wounds to heal quickly and reduces infection risk significantly. This cultivar naturally forms a vase-shaped crown and requires very little pruning once established. In the first few years after planting, your main task is to establish a clear trunk and a balanced framework of branches. Remove any shoots emerging from the lower trunk, and thin out crossing or rubbing branches that will cause damage as they thicken. Always cut back to a main branch or the trunk—don't leave stubs, which invite disease. On mature trees, pruning should be minimal. Remove any dead, diseased or damaged wood as soon as you notice it, cutting back to healthy tissue. If two branches cross and rub, remove the weaker or more awkwardly placed one. You can also take out any vigorous upright shoots (water sprouts) growing from the main branches, as these spoil the tree's elegant shape and rarely flower well. Use clean, sharp secateurs for twigs and small branches up to about 2 cm diameter, and a pruning saw for anything larger. Avoid tearing the bark. For cuts over 3–4 cm, you may choose to apply a wound sealant, though this is debated; good timing and clean cuts are more important. Never top or heavily reduce a flowering cherry—it ruins the form and stresses the tree.

Maintenance

Japanese cherry 'Kanzan' has a moderate water requirement and low overall maintenance once established. Water newly planted trees regularly through their first spring and summer—weekly in dry weather—to help roots settle in. Established trees are fairly drought-tolerant but appreciate deep watering during prolonged dry spells in late spring and summer, especially on free-draining chalky or sandy soils. Avoid overwatering on heavy clay, which can lead to root problems. Feed once a year in March with a general-purpose granular fertiliser (such as Growmore or blood, fish and bone) scattered in a circle around the drip line of the canopy and watered in. A mulch of garden compost or well-rotted manure applied at the same time will improve soil structure and provide a slow nutrient release, but keep mulch a few centimetres away from the trunk. 'Kanzan' is fully hardy across temperate Europe (zones 5b–9a) and needs no winter protection. It flowers reliably in spring, producing masses of double pink blossom on bare branches, though a late hard frost can occasionally damage open flowers. The main pest and disease concerns are aphids in spring, which cluster on soft new growth and can cause leaf curl, and silver leaf disease, a fungal infection that enters through wounds. Prune only in summer to minimise silver leaf risk. Bacterial canker can also affect cherries, causing sunken patches on bark and gummy ooze; remove affected branches promptly. Caterpillars may occasionally chew leaves in summer but rarely warrant treatment. Keep the base of the tree clear of weeds and debris to reduce hiding places for pests and improve air circulation around the trunk.